In a typical communications network, also referred to as e.g. a wireless communications network, a wireless communications system, a communications network or a communications system, a wireless device communicates via a RAN to one or more CNs.
The wireless device may be a device by which a subscriber may access services offered by an operator's network and services outside the operator's network to which the operator's RAN and CN provide access, e.g. access to the Internet. The wireless device may be any device, mobile or stationary, enabled to communicate over a radio channel in the communications network, for instance but not limited to e.g. user equipment, mobile phone, smart phone, sensors, meters, vehicles, household appliances, medical appliances, media players, cameras, Machine to Machine (M2M) device or any type of consumer electronic, for instance but not limited to television, radio, lighting arrangements, tablet computer, laptop or Personal Computer (PC). The wireless device may be portable, pocket storable, hand held, computer comprised, or vehicle mounted devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another device or a server.
Wireless devices are enabled to communicate wirelessly in the communications network. The communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between the devices and a server via the RAN and possibly one or more CNs and possibly the Internet.
The communications network may be described as a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g. a Radio Base Station (RBS), which in some RANs is also called evolved NodeB (eNB), NodeB, B node or base station. A cell is a geographical area where radio coverage is provided by the radio base station at a base station site. The base station communicates with the wireless device(s) within range of the base station.
The Third Generation Partnership Project (3GPP) network may be organized using network sharing. A shared network allows different CN operators to connect to a shared RAN. The operators may share radio network elements and/or radio resources, in addition to the CN nodes. The target shared network is shared between CN operators. To handle network sharing, the 3GPP standard has introduced support for Multi Operator Core Network (MOCN) and Gateway Core Network (GWCN) (see 3GPP TS 23.251) which provides means to share RANs between multiple operators. In GWCN, the CN operators also share CN nodes, such as a Mobile Switching Center (MSC) or Serving General packet radio service Support Node (SGSN), in addition to sharing RAN nodes. In MOCN, only the RAN is shared between the CN operators. The RAN is responsible for the selection of the CN node when the wireless device performs registration procedures like e.g. Location Area Update (LAU), Routing Area Update (RAU) or combined RAU/LAU. In the Release-10 of the 3GPP specification, new procedures have been introduced to re-route a registration to another CN node if the initial selection performed by the RAN was incorrect (see 3GPP TS 23.251).
A routing area is the PS domain corresponding item to a location area. A routing area may be a subdivision of a location area and there may be at least one routing area within the corresponding location area. A routing area is identified by a Routing Area Identifier (RAI) and a location area is identified by a Location Area Identifier (LAI). A PLMN may be divided into location areas and routing areas. A change from routing area to routing area, referred to as a routing area update, is done in a very similar way to a change from location area to location area. The main difference is that the SGSN is the involved node.
When the wireless device is moving, it may be handed over from a source network to a target shared network, e.g. from a source RAN node to a target RAN node. At handover, the connections between the wireless device and the source network are handed over to the target shared network. After a handover, a target shared network selects the PLMN that the wireless device shall register to. PLMN is a network with the objective of providing wireless communication and to interlink the wireless network with the fixed wired network. A PLMN is identified by a PLMN ID comprising a Mobile Country Code (MCC) and a Mobile Network Code (MNC). Each operator providing mobile services may have its own PLMN. PLMNs interconnect with other PLMNs and Public Switched Telephone Networks (PSTNs) for telephone communications or with internet service providers for data and internet access of which links are defined as interconnect links between providers.